Major types of ring-shaped charged particle accelerators include cyclotrons and synchrotrons. With a cyclotron, the orbital radius of an accelerating charged particle increases as its energy rises. On the other hand, with a synchrotron, the strength of the bending magnets increases in synchronization with the rising energy of an accelerating charged particle, and thus the orbit of the accelerating charged particle is kept constant.
Besides being used as high-energy accelerators for electrons (positrons) and protons, synchrotron-type charged particle accelerators and charged particle storage rings are currently being built and operated worldwide as rings for radiation sources of various size (see Non Patent Literature 1 to 5, for example). Also, a large number of synchrotron facilities that accelerate and store protons or carbon ions provided for medical use are being built recently (see Non Patent Literature 6 to 8, for example).
Particle orbits in these synchrotron accelerators disclosed in Non Patent Literature 1 to 8 all close in one cycle. In other words, charged particles in the accelerators return to their original orbit in one cycle around the ring.